Electrodeposition of bright nickel



United States Patent O This invention relates to the galvanic depositionof nickel, and more particularly to the deposition of lustrous andductile nickel deposits from electrolytes of types generally known perso, such as the so-called Watts nickel plating bath containing bothnickel sulfate and nickel chloride, the nickel sulfamate, the nickelfluoroborate type electrolytes, and others.

The afore-mentioned types of nickel plating solutions normally yielddull electrodeposits, but bright deposits can be obtained by theaddition'of certain organic materials in small amounts. It is wellestablished that most desirable lustrous deposits are formed fromsolutions which contain two addition agents, commonly referred to asprimary and secondary brighteners. The secondary brighteners have littleeffect on the appearance of a nickel electrodcposit when employed alone,but they enhance the effect of the primary brighteners and are necessaryfor the fullest brightening elfect of the latter. The common secondarynickel brighteners include alkyl and aryl sulfonic acids, sulfarnides,and sulfimides.

The object of this invention is the provision of novel primarybrighteners which permit the deposition of mirror bright deposits havinggood leveling characteristics, and which are effective in a broadvariety of nickel plating solutions and over an unusually broad range ofoperating conditions. 7

The novel primary nickel plating brighteners of the invention have thegeneral formula R. Rb R R W W R 1% N N wherein R, R,, R R, R" and R aresubstituents attached to a carbon atom of a pyridine ring of thecompound. They are selected from the group consisting of hydrogen,alkyl, lower alkylene, hydroxyalkyl, formyl, halide, alkanoyl, cyano,hydroxy, sulfo, amino, and alkylamino radicals. One substituent of thetwo groups consisting of R, R, and R and R, R" and R? may also be adivalent radical (3 H, attached to two adjacent carbon atoms of saidpyridine ring, forming thus a portion of a benzene ring; and wherein Xis an unsubstituted olefinically unsaturated hydrocarbon chain of 2 to 5carbon atoms. The N-addition products of the above compounds especiallythe lower haloalkyl N-addition compounds are also excellent primarynickel brighteners. Very good results are received with those compoundshaving added bromo alkyl and bromo alkylene groups to the nitrogen atom.

The brighteners of the invention thus are aliphatic hydrocarbons inwhich two hydrogen atoms are replaced by pyridyl, quinolyl, orisoquinolyl radicals. The heterocyclic radicals themselves carry one ormore substituent groups. Substituents which do not interfere with thebrightening effect include alkyl, acetyl, hydroxy, amino, cyano,sulfonate radicals, the functional formyl and car- ICE bonyl groups, andmany more. The quaternary nitrogen addition compounds are as effectiveas 'the free bases. Such addition compounds include the quaternarycompounds formed with alkyl and aryl halides, such as ethyl bromide,ethyl iodide, ethylene bromide ethylene iodide, allyl bromide, allyliodide, dimethyl sulfate, choloroacetone, bromoacetophenon, benzylchloride, a-picolyl iodide.

Representative examples of primary nickel plating brighteners of theinvention are listed in Table I, but the invention is not limited to thespecific examples listed since the brightening efiect is characteristicof'all compounds satisfying the above formulas. The brighteners of theinvention are effective in very small concentrations. As little as 1 mg.per liter has the desired brightening effect. As much as 0.1 gram perliter may be employed without harmful eiiects. Under most practicaloperating conditions brightener concentrations within the range of 0.001to 0.06 grai 1 per liter are preferred to produce the desired mirrorbrightness in a nickel electrodeposit.

in this concentration range, the brighteners of the invention have aparticularly favorable leveling eitect. Deposits produced fromelectrolytes containing the brighteners of the invention tend topreferentially fill polishing scratches and other minor sufaceimperfections. A nickel deposit of an average thickness of 10 microns isusually sufficient to obliterate normal polishing marks. Another unusualcharacteristic property of bright nickel plating solutions containingthe primary brighteners of the invention is the broad range of cathodecurrent densities over which mirror bright nickel deposits are produced.Because of the lack of criticality of the current density, uniformlybright nickel deposits can be formed on objects of complex shape on thesurface of which the cathode current density necessarily varies widely.Yet another distinguishing mark of nickel coatings'deposited fromelectrolytes containing the primary brighteners of the invention in thepreferred concentration range is the ductility of the deposits whichusually permit the nickel plated objects to be deformed after platingwithout the formation of cracks.

It is preferred to provide relative movement between the electrolyte andthe object being nickel plated in an electrolyte of the invention, andany conventional means for agitating the electrolyte or for moving thearticle being plated in the electrolyte, or both, may be employed in theusual manner. Such means include mechanical stirring of the electrolyteor passage of compressed air therethrcugh, cathode rod agitation, andthe like. Fully bright deposits, however, are also formed from theelectrolytes of the invention without any relative movement ofelectrolyte and article. A relatively low current density is advisablein still plating solutions as is well understood and usual in nickelplating. Nickel plating solutions useful for barrel plating producelustrous nickel deposits on small objects plated in bulk when thebrighteners of the invention are added thereto.

The temperature of the electrolyte is immaterial to the brighteningeffect of the brighteners of this invention, and the temperaturescommonly preferred with specific types of nickel plating solutions maybe employed when these solutions contain the brighteners of theinvention. The brighteners are fully efiective even at room temperature,and are stable at the highest temperatures that are in commercial usefor nickel plating at this time. Bright deposits are obtained withoutdifficulty from electrolytes operated at temperatures as high as C.

The pH value of the electrolytes of the invention is not 3 critical. Theprimary brighteners of the invention ensure fully bright nickel depositsover the entire range of hydrogen ion concentrations currently used indecorative nickel plating. More specifically, the brighteners areequally efiective at the relatively extreme pH values of 2.0 and 5.8 andat the more usual pH values of 3.5 to 5.5.

When free of highly reactive substituent radicals, the nickelbrighteners of the invention are stable in conventional nickel platingelectrolytes, and do not form decomposition products which wouldinterfere with bright plating. Nickel plating baths containing thebrighteners of the invention can be operated over extended periodswithout requiring the usual reconditioning treatments.

As is usual with nickel plating brighteners, the bright ening agents ofthe invention are preferably employed jointly with secondarybrighteners. Representative examples of secondary brighteners useful indeveloping optimum deposit properties from the electrolytes of theinvention are listed in Table II. These secondary brighteners includesulfonic acids derived from aliphatic and aromatic compounds, and theamides and imides of such sulfonic acids. The organic addition agents inthe bright nickel plating electrolytes of the invention may furtherinclude surface active agents to prevent porosity due to hydrogenbubbles. All secondary brighteners of Table II may be combined with allprimary brighteners of Table I.

The brightening agents of the invention may be prepared by reacting thecorresponding pyridyl or quinolyl aldehydes with alkyl pyridines oralkyl quinolines at elevated temperatures in the presence of a zincchloride catalyst. The pyridyl and quinolyl alkylenes so prepared may behydrogenated and then reacted with alkyl or aryl halides to form thenitrogen addition compounds by methods well known in themselves. In ananalogous manner the substituted compounds may be prepared.

The reaction is represented by the following equation:

Those compounds of this invention containing a saturated hydrocarbonbridge between the two nucleus may be prepared by one of the threefollowing methods (1) Reaction of ethylene oxide with a lithiumsubstituted pyridyl, quinolyl or isoquinolyl compound in the presence ofwater. For instance N Li N GHQ-CH2 (2) Reaction of alkoxy pyridyl,alkoxy quinolyl or 'alkoxy isoquinolyl compounds with the respectivelithium compounds:

(3) Reaction of chloro methylpyridyl, chloro methylquinolyl orchloromethyl isoquinolin compounds with the respective chlorine freecompounds, according to the following equation Those compounds of thisinvention containing a hydrocarbon bridge of more than two carbon atomsbetween the two nucleus may be prepared by the following reaction:

TABLE I 1,2-di- [Z-pyridyl] ethylene 1,2-di-[4-pyridyl] ethylene 1-[Z-pyridyl] -2- t-pyridyl] ethylene 1,3-di-[2-pyridyl] propylene1,5-di[3-pyridy1]-pentadiene [1,3]

1,3-di-[4-pyridyl]-a-butylene 1,3-di- [4-pyridyl] -b-butylene 1,4-di-[4-pyridyl] -butylene Bis- [4-chloropyridyl-[2] ethylene Bis-[4,6-dichloropyridyl-[2] ethylene Bis- [4-formylpyridyl-[2] ethyleneBis-[3-hydroxyethylpyridyl- [2] ethylene Bis- [4-chloromethylpyridyl-[2]ethylene Bis-[4-acetylpyridyl-[2]] ethylene Bis-[2-ethylpyridyl-4]ethylene Bis-[4-n-pentylpyridyl-2] ethylene Bis-[3-cyanopyridyl- [2]ethylene Bis- 3-hydroxypyridyl- [4] ethylene Bis- [pyridyl-3-sulfonicacid- [2] ethylene Bis- [4-aminopyridyl-[2] ethyleneBis-[4-methylaminopyridyl- [2] ethylene 1,3-di-[2,6-dimethylpyridyl-(4)]propylene 1,2-di-[2-quinolyl] ethylene 1,2-di-[3-quinolyl] ethylene1-[3-quinolyl]-2-[4-quinolyl] ethylene 1,2-di-[4-isoquinolyl] ethyleneBis- [4-formylquinolyl-[2] ethylene Bis- [4-hydroxymethylquinolyl- [2]ethylene Bis-[N-allylN-bromo-pyridine- [2] ethylene Bis[-N-acetonyl-N-chloro-pyridine- [2] ethaneBis-[N-allyl-N-bromo-4-formylpyridine- [2] ethyleneBis-[N-phenacyl-N-iodo-pyridine- [4] ethylene Bis- [N-benzothiazolyl-(2) -methy1-N-iodo-pyridinc- (2) ethylene Bis- [N-pyridyl- (2-methyl-N-chloro-pyridine- (2) ethyleneBis-[N-methyl-N-iodo-4-formylquinolyl-[2] ethylene1,3-di-[N-hydroxyethyl-N-bromo-pyridyl- (4) 1 propylene TABLE IIVinylsulfonic acid Allylsulfonic acid Benzene monosulfonic acid Ortho-,meta-, and para-benzene disulfonic acids Ortho-, meta-, andpara-formylbenzene sulfonic acids 2,4-, 2,5-, and 2,6-formylbenzenedisuli'onic acids Naphthalene mono-, di-, and trisulphonic acids Benzenesulfonarnide Orthoand paratoluene sulfonamides Ortho-, meta-, andparachlorobenzene sultonamides Ortho-sulfimidobenzoic acid The solublesalts of the acids listed as secondary brighteners in Table 11 mayequally be employed, the alkali metal salts, ammonium salts, and nickelsalts being preferred for reasons which will be obvious to those skilledin this art.

The concentration of the secondary brighteners is not critical. They areeffective in concentration ranging from approximately 0.2 gram per literto the solubility limit. Concentrations between 0.5 and 5.0 grams perliter are generally preferred.

The following examples are representative of electrolytes and operatingconditions employed for producing bright nickel electrodeposits in thepresence of the primary brighteners of the invention, but it is to beunderstood that the use of the brighteners is not limited to theelectrolyte compositions of the examples, nor 'to the specific generaltypes of nickel plating solutions described for the purpose of thedisclosure.

Example I Nickel sulfate grams per liter 260 Nickel chloride ....do 50Boric acid do 40 Sodium o-formylbenzene sulfonate do 1.0 Dibenzenesulfirnide do 1.0 Bis-[N-allyl-N-bromo-pyridyl-[2]1 ethylene grams perliter 0.007 Temperature C 50 pH 4.0 Cathode current density, averageamps./dm. 4.0 Cathode current density, actual do 0.5-6.0

Example II Nickel sulfate "grams per liter 240 Nickel chloride do 80Boric acid do 40 Sodium vinyl sulfona-te do 2.0 Sodiumo-sulfimidobenzoate do 5.0 l[3-pyridyl]-2-[4-pyridyl]-ethylene do 0.006Temperature C 60 pH 4.2 Cathode current density, average amps./dm. 6.0

Cathode current density, actual amps./dm. 0.5 to 8.0

Example Ill Nickel fluoborate grams per liter 340 Nickel chloride doSodium o-formylbenzene sulfonate do 1.0 Bis-p-chlorobenzene sulfimide do1.0 1,2-di-2-quinolyl ethylene do 0.006 Temperature C 60 pH 3.5 Cathodecurrent density, average amps./dm. 15.0

Cathode current density, actual "amps/din? 05-15 .0

6 Example lV Nickel sulfate grams per liter 200 Sodium chloride do 30Boric acid do 30 Sodium vinylsulfonate do 1.0 p-Toluene sulfonamide do0.4- Bis-[4-formylpyridyl-[2]] ethylene do 0.005 Temperature C 20 pH 4.6Cathode current density, average amps./dm. 2.0

Cathode current density, actual amps./dm. 0.5-3.0

Example V Nickel sulfamate grams per liter 400 Boric acid do 30 Sodium1,3,6-naphthalenetrisulfonate do 3.0 p-Chlorobenzene sulfonamide do 1.01,2-di-[4-pyridyl] ethylene do 0.01 Temperature C 55 pH 5.5 Currentdensity "amps/din? 10 In the preceding examples the primary andsecondary brighteners specifically set forth may be replaced byequimolecular amounts of the primary and secondary brightenersrespectively listed in Tables I and 11, either singly or in combination.More specifically, the 1,2-di-4-pyridyl ethylene employed in Example VImay be replaced by an equimolecular amount of any one of the compoundslisted in Table I or by an equivalent amount of a mixture composed oftwo or more compounds listed in Table I in any desired proportion.Similarly, the secondary brighteners of Table II may be substitutedsingly or in mixtures for the secondary brighteners specifically setforth in Examples I and VI.

Substantially mirror bright deposits are produced in the methods ofExamples 1 to VI, and in methods similar to those of these examples,'butmodified by the substitution of primary or secondary brighteners as setforth hereinabove. The brightness of the coatings is not materiallyaffected by the cathode current density. Objects of very complex shapeon the surface of which the actual current density varies by more thanone order of magnitude are uniformly coated by a lustrous nickeldeposit.

Temperature, current density,'pli, and other factors are relevant onlyas far as they influence the basic character- .istics of the platingsolutions in a known manner. These factors are without practicalsignificance for the brighting effect of the primary brighteners of theinvention.

The brighteners. of the invention produce lustrous nickel deposits instill tank plating, in conveyor plating on objects traveling through theelectrolyte at relatively slow speeds, in high speed automatic wireplating installations, and on small objects plated in bulk in a platingbarrel.

Surface active agents such as wetting agents, antifoam agents, and otheraddition agents conventionally employed in this art are generallycompatible with the brightening agents of the invention, and thoseskilled in the art Will find that the relatievly inert brighteners ofthis invention do not interfere with the normal operatingcharacteristics of otherwise conventional electrolytes.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the invention rbe practiced otherwise than as specifically described:

What is claimed is: a

1. A nickel plating electrolyte containing between about 0.001 and about0.1 grams per liter of a primary brightener selected from the groupconsisting of compounds of the formula W h td 7 wherein the substituentsR, R R R, R" and R' are radicals attached to a carbon atom of a pyridinering of said compound, and are selected from the group consisting ofhydrogen, lower alkyl, lower alkylene, lower hydroXyalkyl, formyl,halide, lower haloalkyl, lower alkanoyl, cyano, hydroxy, sulfo, amino,and lower alkylamino radicals; wherein one substituent of the two groupsconsisting of R, R and R and R, R and R may also be a divalent radical C11 attached to two adjacent carbon atoms of said pyridine ring, formingthus a portion of a benzene ring; and wherein X is an unsubstitutedolefinically unsaturated hydrocarbon chain of two to five carbon atoms;and the lower haloalkyl N addition products of said compounds.

2. A nickel plating electrolyte according to claim 1, wherein theconcentration of said primary brightner is not substantially greaterthan 0.06 grams per liter.

3. A nickel plating electrolyte containing as a primary brightnerbetween about 0.001 and about 0.1 gram per liter of1,2-dipyridyl-ethylene.

4. A nickel plating electrolyte containing as a primary brightcnerbetween about 0.001 and about 0.1 gram per liter of1,2-diquinolyl-ethylene.

5. A nickel plating electrolyte containing as a primary brightenerbetween about 0.001 and about 0.1 gram per liter ofl,2-diisoquinolyl-ethylene.

6. A nickel plating electrolyte containing as a primary brightenerbetween about 0.001 and about 0.1 gram per liter of1,Z-dipy-ridyl-ethylene-N-lower haloalkyl addition compound.

7. A nickel plating electrolyte containing as a primary brightenerbetween about 0.001 and about 0.1 gram per liter of1,2-diquinolyl-ethylene-N-lower haloalkyl addition compound.

8. A nickel plating electrolyte containing as a primary brightenerbetween about 0.001 and about 0.1 gram per liter of1,2-diisoquinolyl-ethylene-N-lower haloalkyl addition compound.

9. A nickel plating electrolyte containing as a primary brightenerbetween about 0.001 and about 0.1 gram per liter of a compound of theformula Ra RI! XX XX r t a N N wherein the substituents R, R R R, R andR" are radicals attached to a carbon atom of a pyridine ring of saidcompound, and are selected from the group consisting of hydrogen, loweralkyl, lower alkylene, lower hydroxyalkyl, formyl, halide, lowerhaloalkyl, lower alkanoyl, cyano, hydroxy, sulfo, amino, and loweralkylamino radicals; wherein one substituent of the two groupsconsisting of R, RI and R and R, R" and R' may also be a divalentradical O l-I attached to two adjacent carbon atoms of said pyridinering, forming thus a portion of a benzene ring; and wherein X is anunsubstituted olefinically unsaturated hydrocarbon chain of two to fivecarbon atoms; and the lower haloalkyl N addition products of saidcompounds; said nickel plating electrolyte containing a secondarybrightener selected from the group consisting of viny sulfonic acid,allylsulfonic acid, benzene monosulfonic acid, ortho-, meta-, andpara-benzene disulfonic acids, ortho-, meta, and paraformylbenzenesulfonic acids, 2,4-, 2,5-, and 2,6-formylbenzene disulfonic acids,naphthalene mono-, di-, and trisulfonic acids, benzene sulfonamide,orthoand para-toluene sulfonamides, ortho-, meta-, and parachlorobenzenesulfonamides, orthosulfimidobenzoic acid, dibenzene sulfimide,bis-(o-chlorobenzene) sulfimide, m-di-sulfonylbenzene-bis-N-benzenesulfimide, and salts of said acids.

10. A nickel plating electrolyte containing as a primary brightenerbetween about 0.001 and about 0.1 gram per 8.. liter of lower haloalkylN-addition compound of a compound having the formula Ra Rb R I XX R Xij-R wherein the substituents R, R,,, R R, R, and R are radicals attachedto a carbon atom of a pyridine ring of said compound, and are selectedfrom the group consisting of hydrogen, lower alkyl, lower alkylene,lower hydroxyalkyl, formyl, halide, lower haloalkyl, lower alkanoyl,cyano, hydroxy, sulfo, amino, and lower alkylamino radicals; wherein onesubstituent of the two groups consisting of R, R, and R and R, R and R"may also be a divalent radical 0 H, attached to two adjacent carbonatoms of said pyridine ring, forming thus a portion of a benzene ring;and wherein X is an unsubstituted olefinically unsaturated hydrocarbonchain of two to five carbon atoms.

11. A nickel plating electrolyte containing as a primary brightenerbetween about 0.001 and about 0.1 gram per liter of a compound of theformula a, Rb R a" W W t jiRI/I /N\ /N\ Alk Hal All: Hal

wherein the substituents R, R,,, R R, R, and R' are radicals attached toa carbon atom of a pyridine ring of said compound and are selected fromthe group consisting of hydrogen, lower alkyl, lower alkylene, lowerhydroxyalkyl, formyl, halide, lower haloalkyl, lower alkanoyl, cyano,hydroxy, sulfo, amino, and lower alkylamino radicals; wherein onesubstituent of the two groups consisting of R, R and R and R, R and Rmay also be a divalent radical C H attached to two adjacent carbon atomsof said pyridine ring, forming thus a portion of a benzene ring; andwherein X is an unsubstituted olefinically unsaturated hydrocarbon chainof two to five carbon atoms; alk is a lower alkyl radical; and Hal is ahalide radical.

12. A nickel plating electrolyte containing as a primary brightenerbetween about 0.001 and about 0.1 gram per liter of a compound havingtwo pyridine rings joined by an unsubstituted olefinically unsaturatedhydrocarbon chain of two to live carbon atoms and attached to respectivecarbon atoms of said pyridine rings.

13. A method of electrodepositing a bright nickel coating on an articlewhich comprises making the article the cathode in a nickel platingelectrolyte containing between about 0.001 and about 0.1 gram per literof a primary brightener selected from the group consisting of compoundsof the formula XX XX wherein the substituents R, R,,, R R, R, and R areradicals attached to a carbon atom of a pyridine ring of said compound,and are selected from the group consisting of hydrogen, lower alkyl,lower alkylene, lower hydroxylalkyl, formyl, halide, lower haloalkyl,lower alkanoyl, cyano, hydroxy, sulfo, amino, and lower alkylaminoradicals; wherein one substituent of the two groups consisting of R, R,and R and R, R and R' may also be a divalent radical of C H attached totwo adjacent carbon atoms of said pyridine ring, forming thus a portionof a benzene ring; and wherein X is an unsubstituted olefinicallyunsaturated hydrocarbon chain of two to five car bon atoms; and thelower haloalkyl N addition products of said compounds.

14. A method according to claim 13, wherein said electrolyte has a pHvalue not substantially higher than 5.5.

15. A nickel plating electrolyte containing as a primary brightenerbetween about 0.001 and about 0.1 gram per liter of a compound of theformula wherein A is a radical selected from the group consisting ofpyridyl, quinolyl, isoquinolyl, chloropyridyl, chloroquinolyl,chloroisoquinolyl, dichloropyridyl, dichloroquinolyl,dichloroisoquinolyl, allylpyridyl, allylquinoyl, allylisoquinolyl,formylpyridyl, formylquinonyl, formylisoquinolyl, lower alkylpyridyl,lower alkylquinolyl, lower alkylisoquinolyl, lower oxyalkypyridyl, loweroxalkylquinolyl,

lower oxyalkylisoquinolyl and the nitrogen addition compounds thereof;and wherein X is an unsubstituted olefinically unsaturated hydrocarbonchain of two to five carbon atoms.

References Cited by the Examiner UNITED STATES PATENTS 2,839,460 6/58Foulke 204-49 2,881,120 4/59 Towle -2 204 49 10 3,008,883 11/61 Passal204-49 JOHN H. MACK, Primary Examiner.

MURRAY TILLMAN, JOHN R. SPECK, WINSTON A.

DOUGLAS, Examiners.

1. A NICKEL PLATING ELECTOLYTE CONTAINING BETWEEN ABOUT 0.001 AND ABOUT0.1 GRAMS PER LITER OF A PRIMARY BRIGHTENER SELECTED FROM THE GROUPCONSISTING OF COMPOUNDS OF THE FORMULA